Torque wrench



C. W. HART TORQUE WRENCH April 6, 5 43.

Filed Jan. 10, 19412 n I $H w, m u k m I m 2 Km mm wfh m lm m h B I JV, ..Q\

Patented Apr. 6, 1943 UNITED STATES PATENT OFFICE Claims.

(Granted under the act of March 3, 1883, 'as

amended April 30, 1928; 370 O. G. 757) This invention relates to an improvement in torque indicating wrenches. It has for its primary objective the provision of an improved wrench possessing a graduated torque measuring scale indicating torque obtained to the operator 5 through his senses of sound and touch and not through his sense of sight.

Another object is to provide a method of measuring torque in situations where the operator cannot plainly see the Wrench, the work, or both. Such a situation often occurs due to poor lighting, or where the working space is restricted and interferences are interposed between the operator and his work.

Another object is to provide a Wrench of greater simplicity of design and more rugged and inexpensive than any of its type known at present.

Still another object is to provide a design of torque indicating means which is applicable to 0 any type of wrench regardless of its size or shape without materially increasing its size or cost due to the addition of the torque measuring device.

A further object is to provide a torque indicating wrench of conventional size and design which may be operated with greater speed and accuracy than is attained with prior wrenches. The manner whereby this increased speed and accuracy are obtained is somewhat analogous to that in which touch typing on a typewriter is. an improvement over sight typing.

Another object is to provide a wrench which is most suitable for the type of personnel and work where it is used. In the overhaul of most machinery, and particularly steam plants and internal. combustion engines where torque accuracy is paramount, there are usually numerous nuts and bolts to be tightened. It requires less effort to obtain correct torque settings with this wrench than with former ones. This tends to prevent laxness due to monotony after several hours of intensive work.

Still another object is to provide a type of torque wrench which may be manufactured so as to be particularly adapted to work on a specific machine. a given mechanism having a special wrench or wrenches manufactured to suit its particular needs. Such a special Wrench may be calibrated during manufacture so as to emit sounds clicks when the correct setting up torques are reached for each of the various nuts and bolts employed in the mechanism for which the wrench is designed.

Other objects and advantages will be apparent 0 cross section than the shank as the description progresses and by reference to the drawing wherein:

Fig. 1 is a plan View of at torque wrench constructed in accordance with the present invention.

Fig. 2 is a side elevation view of the wrench shown in Fig. 1.

Fig. 3 is a transverse sectional view taken on line 3-3 of Fig. 2.

Fig. 4 is a transverse sectional view taken on line 3-3 of Fig. 2 showing method of varying the pitch of the pitch teeth so as to emit clicks each time the applied torque is increased by a predetermined unit of torque, and

Fig. 5 is a transverse sectional view showing a modified form of the device wherein the single tooth is on the leaf spring and the pitch teeth are on the shank.

Fig. 6 is a view similar to Fig. 5 showing a further modification in which the pitch teeth on the shank are of varying pitch.

Referring to the drawing, the improved torque wrench is shown as a standard type double box socket and open end wrench comprising a shank l0 having an open jaw bolt or nut engaging portion II at one end and a closed double box hexagonal socket portion l2 at the other end thereof. The shank I0 is formed with an intermediate flattened flexible portion I3 of smaller ID. This intermediate portion I3 is adapted to be flexed when force is applied to the wrench. The amount of bending of this portion l3 of the wrench is audibly indicated by means of a leaf spring M which is rigidly secured at one end to the shank H) by a screw l5. The leaf spring I4 is pro vided at its other end with a series of pitch teeth l6. These pitch teeth l6 are engaged in mesh under spring pressure of the leaf spring M with a single tooth or ridge ll which is an integral part of the wrench shank Hi.

In operation, when force is applied to the wrench in tightening a nut or bolt the resilient central reduced portion l3 will be flexed. This causes the pitch toothed portion [6 of the spring I4 to snap or ride over the ridge I! one or more teeth, according to the amount of force applied. This will give a click or series of clicks which may be felt as well as heard by the operator. When the force is released the flexible portion i3 returns to its original shape, bringing the ridge I'l into its zero or central mesh position with the pitch teeth [6 of leaf spring l4.

Calibration of this wrench in terms of any torque units desired may be accomplished by testing the wrench against known torques and thus obtaining a table or curve of clicks againstv torque. Wrenches may be made to give a click each time the torque applied is increased by a predetermin d amount of torque. Such a wrench would give clicks at say 10. 20, 30. etc. pound feet of torque. This is accomplished by varying the distance pitchl between the teeth a they get further removed either side of the zero torque or central mesh position. Fig. 4 shows the leaf spring l4 provided with teeth Iii of varying pitch provided on the shank portion of the wrench.

This wrench will operate equally well with the positions of the pitch teeth and the ridge interchanged. Details of such a wrench are shown in Fig. 5 in which a plurality of pitch teeth I! are provided on the shank and a single tooth l6" provided on the leaf spring 14.

As mentioned in the objects. wrenches of this type may be calibrated for use with a particular mechanism. Such use in factory assembly lines and the like appears to be the field wherein this Wrench would probably be most extensively used.

A change in the cross sectional shape or area of the wrench causes a corresponding change in the torque range over which the Wrench will properly measure torque before the elastic limit of the portion of reduced cross sectional area is approached.

It is to be understood that the form of my invention, herewith shown and described, is to be taken a a preferred example of same, and that various changes in the shape, size and arrangement of the parts may be resorted to without departing from the spirit of my invention or the scope of the subjoined claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Having ihus set forth and disclosed the nature of this invention. what is claimed is:

l. A sound and touch operated torque indicating wrench comprising a shank having a flexible portion. a leaf spring fixed to said shank at one end of said flexible portion bridging this portion. pitch teeth on the free end of said leaf spring.

and a raised tooth on the shank adjacent to the pitch teeth of the leaf spring pressed into mesh contact with said teeth under spring pressure afforded by the leaf spring. whereby the flexing of said flexible portion of the said shank will cause said fixed tooth and said pitch teeth to move relative to one another with a snapping action when torque is applied to said wrench.

2. A sound and touch operated torque indicat ing wrench comprising a shank having a flexible portion, a leaf spring rigidly fixed to said shank at one end of said flexible portion bridging this portion. a raised tooth at the free end of said leaf spl'illfl. pitch teeth rigidly attached to the wrench adjacent to the said raised tooth on the leaf spring and coming into mesh contact with same under pring pressure afforded by the leaf spring whereby the flexing of said flexible portion of said shank will cause the said fixed tooth and the said pitch teeth to move relative to one another with a snapping action when torque is appliedto the said wrench.

3. A sound and touch operated torque indicating wrench comprising a shank having a central flexible portion. a raised tooth on the shank adjacent one end of said flexible portion, a leaf spring rigidly fixed to the shank at the other end of the said flexible portion bridging this portion and tree at its other end, teeth of graduated pitch on the free end of said leaf spring adjacent to said raised tooth on the shank and coming into mesh contact with same under leaf spring pressure, whereby flexing of said flexible portion will cause said raised tooth and graduated teeth to move relative to each other with a grating action producing a number of audible clicks proportional to the torque applied by the wrench.

4. A sound and touch operated torque indicating wrench comprising a shank having a central flexible portion, teeth of graduated pitch on the shank adjacent one end of said flexible portion, a leaf spring rigidly fixed to the shank at the other end of the said flexible portion bridging this portion and free at its other end, a raised tooth on the free end of said leaf spring adjacent to said teeth of graduated pitch on the shank and coming into mesh contact with same under leaf spring pressure, whereby flexing of said flexible portion will cause said raised tooth and graduated teeth to move relative to each other with a grating action producing a number of audible clicks proportional to the torque applied by the wrench.

5. A sound and touch operated torque indicating wrench comprising a shank member having a flexible portion, a leaf spring member having one of its ends fixed to said shank member at one end of said flexible portion and bridging this portion. pitch teeth onone of said members adjacent the free end of the spring member, and a 

